(a) Field of the Invention
The present invention relates to a method and an apparatus for dynamically allocating a resource. More particularly, the present invention relates to a method and an apparatus for allocating a resource to control inter-cell interference in a wireless communication system including a plurality of cells.
(b) Description of the Related Art
In general, in a wireless communication system, in order to increase capacity of the system, an entire service area is divided into a plurality of cells to form a multi-cell. In each cell, a base station for providing a service to a terminal positioned in the cell is provided.
In such a cellular system, in order to increase the capacity of the system, frequency use efficiency must be maximized. For this purpose, cells are designed to commonly use an entire frequency band. When adjacent cells use the same frequency band, since a sub-channel formed of an orthogonal frequency is allocated to each user, there is no interference in one cell, however, interference is generated between cells. The above phenomenon is referred to as inter-cell interference.
Particularly, in terminals positioned in a center region of a cell, since intensity of a signal received from another cell is small and that of a signal received from a serving cell is large, the inter-cell interference does not significantly matter. However, in terminals positioned in a cell edge of the cell, since intensity of a signal received from an adjacent cell is large and that of the signal received from the serving cell is small, the inter-cell interference significantly deteriorates communication performance.
In order to prevent the communication performance of the terminals positioned in the cell edge of the cell from being deteriorated, in a conventional art, a fractional frequency reuse (FFR) technique is suggested.
In the FFR technique for allocating a resource to remove the inter-cell interference in a frequency region, a cell is divided into a center region and a cell edge and a frequency reuse factor of terminals positioned in the center region is set up to be different from that of terminals positioned in the cell edge. However, since a frequency use band of the terminals positioned in the center region and the edge cell is limited in the FFR technique, there is a drawback in that a frequency selective gain is limited. For example, when deep fading occurs in the terminals positioned in the cell edge in an allocated frequency sub-band, performance of the terminals is severely deteriorated. In addition, in the cell edge region, due to a large reuse factor, entire spectral efficiency is limited.
A fractional time reuse (FTR) technique for controlling interference through time scheduling coordination among base stations is suggested as a solution for the problem of the FFR technique.
In the FTR technique, a cell is divided into a center region and a cell edge, and all base stations serve terminals using an entire frequency band in all time slots in the center region and only one base station between adjacent base stations serves the terminals using the entire frequency band in an allocated specific time slot in the cell edge. In the FTR technique, a frequency selective gain is provided to the terminals positioned in the center region and the cell edge of the cell so that performance of the terminals may be improved.
However, such interference coordination using the static FFR and FTR techniques is not adaptive to changes in user distribution of the system and a load level of a base station.